In the anionic polymerization of a lactam, especially caprolactam, an anionic polymerization catalyst and an activator (or promoter) are typically present. Various kinds of activators are disclosed in the art.
One proposal for an activated anionic catalytic polymerization process is described in U.S. Pat. No. 3,304,291. The activator used therein consists of organic compounds having at least a 2 to 12 carbon atom containing radical and being an N-substituted compound of at least one urea, thiourea or guanidine radical.
An improvement thereon for producing polylactams having a higher notch impact strength includes conducting the activated anionic catalyzed lactam polymerization process in the presence of a quantity of a polyether soluble in the molten lactam, or the mixture of lactams, being polymerized. The polyether is limited to at most about 25% by weight of the quantity of the lactam to be polymerized, otherwise the resultant polylactams possess poor mechanical properties.
An isocyanate promoter having at least one isocyanate compound has been used in an anionic catalytic polymerization of a lactam conducted in the presence of a polyether soluble in molten lactam.
As further described in U.S. Pat. No. 3,704,280, it is required that the absolute number of hydroxyl (OH) groups contained in the polyether is greater than the absolute number of isocyanate groups contained in the isocyanate employed.
Another improved process for the anionic catalytic polymerization of lactams, aided by one or more promoters, is described in U.S. Pat. No. 3,770,689 and includes adding to the reaction mixture one or more polyether compounds having etherfied hydroxyl groups which are soluble in the molten lactam or lactam mixture. Conventional promoters suitable for use therein include polymers having backbone chains permanently terminated on at least one end by a promoter function. Generally the promoter functional groups or substituents are similar to monomeric promoters such as acid-chloride groups, N-carbonyl-sulfonamide groups, N-carbonyl-urea groups and acid-anhydride groups.
U.S. Pat. No. 3,987,033 describes a composition prepared by reacting an aromatic diisocyanate with a tri-primary hydroxyl alcohol and subsequently reacting this product with a mixture of a hydroxy component such as a phenol.
U.S. Pat. No. 4,171,305 describes pure cyrstals of .epsilon.-caprolactam diblocked .omega.,.omega.'-diisocyanato-1,3-dimethylbenzene. The product is used as a hardener in a powder coating composition.
U.S. Pat. No. 4,211,699 describes isocyanate diol adducts derived from an amino diol or a hydrazine diol and an organic diisocyanate. Using the isocyanate diols for producing self-crosslinkable and/or self-crosslinked polyurethanes is described.
U.S. Pat. No. 3,018,273 describes a process for in situ polymerizing caprolactam in the presence of an organomagnesium initiator compound, wherein an N,N diacyl compound is used as a promoter. Preferably, the N,N diacyl compounds are N-substituted imides or cyclic imides of dicarboxylic acids. Preferably, the N,N diacyl compounds have molecular weights not exceeding 1000 in order to preclude the presence of large inert groups in the promoters. More preferably the N,N diacyl compounds have molecular weights not exceeding 500.
British Pat. No. 1,067,153 describes a process for preparing nylon-block-copolymers by anionically polymerizing caprolactam in the presence of an isocyanate-terminated polypropylene glycol and a potassium based catalyst. In this process a nylon block copolymer containing at least one polyetherblock is formed.
In the U.S. Pat. Nos. 4,223,112, 4,031,164, 3,862,262, and 4,034,015 various aspects of the preparation of nylon block copolymers from caprolactam in the presence of an acyl lactam activator are described. U.S. Pat. Nos. 4,223,112 and 4,031,164 describe lactam-polyol-polyacyl-lactam block-terpolymers having a specified ratio of the various components. More particularly, U.S. Pat. No. 4,031,164 discloses the use of 18 to 90% by weight of polyol blocks in the terpolymer. U.S. Pat. No. 3,862,262 describes lactam-polyolacyl-polylactam block-terpolymers, and U.S. Pat. No. 4,034,015 is directed to lactam-polyol-polyacylactam or lactam-polyol-acyl-polylactam block terpolymers having at least about 5% ester end group termination.
U.S. Pat. No. Re 30,371 describes the preparation of polyester-polyamide compounds by condensation of an alcohol with acyl lactams in the presence of at least one of a metal or metal compound. The metal or metal component of the metal compound is selected from Group IA, IIA, IIB and IIIA of the Periodic Table.
The published (Dec. 22, 1982) European patent application Nos. 67693 and 67694, describe specific lactam compounds based upon various kinds of hydroxy compounds, whereas the European patent application Nos. 67694 and 67695 laid open to public inspection on Dec. 22, 1982 describe the use of such lactam compounds in the preparation of nylon block copolymers.
Preparation of nylon compositions by anionically polymerizing at least 75% lactam with up to about 25% of an epoxy component in the presence of a basic catalyst and promoter are disclosed in U.S. Pat. No. 4,400,490. The promoters are those typically used in the anhydrous polymerization of lactams.
A paper by Sibal et al, "Designing Nylon 6 Polymerization Systems", apparently was presented in part at the 2nd International Conference on Reactive Polymer Processing, Pittsburg, PA in November 1982. In connection with the anhydrous anionic polymerization of caprolactam, Sibal et al apparently suggest preparing a cocatalyst or initiator by reacting isocyanate with dried caprolactam at 80.degree. C. Initially the caprolactam may be heated and about 20% thereof boiled off with the dry residue portion being reacted with an isocyanate, the isocyanate being obtained by slowly reacting 1 mole polypropylene glycol (M.W. 2000) with 2 moles hexamethylene diisocyanate. However, this work is said to be incomplete and it is clear that further work is said to be needed to determine reaction conditions, and other process-product characteristics/parameters as well as the processability of any polylactam produced using such an experimental activator.
The nylon block copolymers prepared when using an activator of this kind have various disadvantages. Such copolymers are deficient in thermal resistance, heat distortion temperature and solvent resistance characteristics. Furthermore, the so-called "heat sag" of such copolymers, a measure indicating the product's ability to withstand heat treatment without being deformed, is insufficient. The product cannot withstand the 160.degree. C. and higher temperatures in a curing oven for automobile paints. Finally, an improvement in the impact resistance (Charpy or Izod) of these products is required to make them suitable for application where impact resistance is required.